Method of transmitting scheduling request in a wireless communication system

ABSTRACT

A method and apparatus for requesting uplink resources in a wireless communication system is provided. A user equipment determines whether a scheduling request for requesting uplink resources is triggered. If the scheduling request is triggered, the user equipment transmits a first set of frequency domain sequences and a second set of frequency domain sequences in a subframe.

This application is a continuation of U.S. patent application Ser. No.15/141,195, filed Apr. 28, 2016, now allowed, which is a continuation ofU.S. patent application Ser. No. 13/926,754, filed Jun. 25, 2013 (nowU.S. Pat. No. 9,357,530, issued May 31, 2016), which is a continuationof U.S. patent application Ser. No. 13/449,130, filed Apr. 17, 2012 (nowU.S. Pat. No. 8,509,178, issued Aug. 13, 2013), which is a continuationof U.S. patent application Ser. No. 12/591,091, filed Nov. 6, 2009 (nowU.S. Pat. No. 8,179,857, issued May 15, 2012), which is a continuationof U.S. patent application Ser. No. 12/451,124, filed Oct. 27, 2009 (nowU.S. Pat. No. 7,852,743, issued Dec. 14, 2010), which is a 35 U.S.C. §371 National Stage filing of International Application No.PCT/KR2008/004087, filed Jul. 11, 2008, and which claims priority toKorean Application No. 10-2007-0069991, filed on Jul. 12, 2007, andKorean Application No. 10-2007-0103661, filed Oct. 15, 2007, all ofwhich are incorporated by reference in their entirety herein.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method of transmitting a scheduling request on anuplink control channel in a wireless communication system.

BACKGROUND ART

Third generation partnership project (3GPP) mobile communication systemsbased on a wideband code division multiple access (WCDMA) radio accesstechnology are widely spread all over the world. High-speed downlinkpacket access (HSDPA) that can be defined as a first evolutionary stageof WCDMA provides 3GPP with a radio access technique that is highlycompetitive in the mid-term future. However, since requirements andexpectations of users and service providers are continuously increasedand developments of competing radio access techniques are continuouslyin progress, new technical evolutions in 3GPP are required to securecompetitiveness in the future.

An orthogonal frequency division multiplexing (OFDM) system capable ofreducing inter-symbol interference with a low complexity is taken intoconsideration as one of next generation (after 3G) systems. In the OFDMsystem, serial input data symbols are converted into N parallel datasymbols and are carried and transmitted on separate N subcarriers. Thesubcarriers maintain orthogonality in a frequency dimension. Orthogonalfrequency division multiple access (OFDMA) is a multiple access schemein which multiple access is achieved by independently providing some ofavailable subcarriers to a plurality of users in a system using the OFDMas a modulation scheme.

One of primary problems of the OFDM/OFDMA system is that apeak-to-average power ratio (PAPR) can be significantly large. The PAPRproblem is that a peak amplitude of a transmit (Tx) signal issignificantly larger than an average amplitude. This is caused by thefact that OFDM symbols are N sinusoidal signals overlapping on differentsubcarriers. In particular, since the PAPR is related to batterycapacity, the PAPR is problematic when a user equipment (UE) issensitive to power consumption. The PAPR needs to be reduced to decreasepower consumption.

A single carrier-frequency division multiple access (SC-FDMA) system isone of systems proposed to reduce the PAPR. An SC-FDMA is a combinationof a single carrier-frequency division equalization (SC-FDE) and afrequency division multiple access (FDMA). The SC-FDMA has a similarcharacteristic with an OFDMA in that data is modulated and demodulatedin a time domain and a frequency domain by using a discrete Fouriertransform (DFT). However, the SC-FDMA is advantageous over the OFDMA interms of Tx power saving due to a low PAPR of a Tx signal. Inparticular, regarding the use of batteries, the SC-FDMA is advantageousin uplink communication in which communication is made to a base station(BS) from a UE sensitive to Tx power.

A wide coverage is important when the UE transmits data to the BS.Although a bandwidth of Tx data is small, power can be concentrated inthe wide coverage. The SC-FDMA system provides a signal with littlevariation, and thus has a wider coverage than other systems when thesame power amplifier is used.

In order to implement various transmission or reception methods toachieve high-speed packet transmission, transmission of a control signalon time, spatial, and frequency domains is an essential andindispensable factor. A channel for transmitting the control signal isreferred to as a control channel. An uplink control signal may bevarious such as an acknowledgement (ACK)/negative-acknowledgement (NACK)signal which is a response for downlink data transmission, a channelquality indicator (CQI) indicating downlink channel quality, a precodingmatrix index (PMI), a rank indicator (RI), etc.

One example of the control signal is a scheduling request. Thescheduling request is used when a UE requests a BS to allocate an uplinkradio resource. The scheduling request is a sort of preliminaryinformation exchange for exchanging uplink data. The UE first transmitsthe scheduling request and is allocated with an uplink radio resource.Thereafter, the UE transmits uplink data to the BS. When in an idlemode, the UE can transmit an uplink radio resource allocation requestthrough a conventional random access process. However, when in aconnected mode, a service may be delayed if the UE transmits the uplinkradio resource allocation request through the conventional random accessprocess. This is because the random access is a contention basedprocess, and thus allocation of the uplink radio resource can bedelayed. Therefore, when in the connected mode, the scheduling requestmay be transmitted through a control channel in order to provideeffective resource allocation in a more reliable and rapid manner.

Compatibility with another control channel for transmitting anothercontrol signal has to be taken into consideration when the schedulingrequest needs to be transmitted on an uplink control channel. Inaddition, capacity of the control channel for transmitting thescheduling request has to be also taken into consideration.

Accordingly, there is a need for a control channel having an effectivestructure for transmitting a scheduling request.

DISCLOSURE OF INVENTION Technical Problem

A method is sought for requesting a radio resource for uplinktransmission on an uplink control channel in a wireless communicationsystem.

A method is also sought for transmitting a scheduling request which isused to request a radio resource for uplink transmission in a wirelesscommunication system.

Technical Solution

In an aspect, a method of transmitting a scheduling request which isused to request a radio resource for uplink transmission in a wirelesscommunication system is provided. The method includes configuring anuplink control channel for transmission of a scheduling request in asubframe, the subframe comprising two consecutive slots, a slotcomprising a plurality of single carrier-frequency division multipleaccess (SC-FDMA) symbols, the scheduling request being carried bypresence or absence of transmission of the uplink control channel, andtransmitting the scheduling request on the uplink control channel,wherein configuring the uplink control channel comprises dividing theplurality of SC-FDMA symbols in the slot into a first set of SC-FDMAsymbols and a second set of SC-FDMA symbols, mapping each of firstfrequency domain sequences to each SC-FDMA symbol in the first set, thefirst frequency domain sequences being generated by cyclic shifts of abase sequence, mapping each of second frequency domain sequences to eachSC-FDMA symbol in the second set, the second frequency domain sequencebeing generated by cyclic shifts of the base sequence, spreading thefirst frequency domain sequences in the first set with a firstorthogonal sequence, the first orthogonal sequence having a length equalto the number of SC-FDMA symbols in the first set, and spreading thesecond frequency domain sequences in the second set with a secondorthogonal sequence, the second orthogonal sequence having a lengthequal to the number of SC-FDMA symbols in the second set.

The two consecutive slots in the subframe may use different subcarriers.The length of the first frequency domain sequence and the length of thesecond frequency domain sequence may equal to the number of subcarriersin one SC-FDMA symbol.

In another aspect, a method of transmitting a scheduling request whichis used to request a radio resource for uplink transmission in awireless communication system is provided. The method includesconfiguring an uplink control channel for transmission of a schedulingrequest in a plurality of SC-FDMA symbols, the scheduling request beingcarried by presence or absence of transmission of the uplink controlchannel, and transmitting the scheduling request on the uplink controlchannel, wherein configuring the uplink control channel comprisesdividing the plurality of SC-FDMA symbols into a first set of SC-FDMAsymbols and a second set of SC-FDMA symbols, mapping each of firstfrequency domain sequences to each SC-FDMA symbol in the first set, thefirst frequency domain sequence being generated by cyclic shifts of abase sequence, mapping each of second frequency domain sequences to eachSC-FDMA symbol in the second set, the second frequency domain sequencebeing generated by cyclic shifts of the base sequence, spreading thefirst frequency domain sequences in the first set with a firstorthogonal sequence, the first orthogonal sequence having a length equalto the number of SC-FDMA symbols in the first set, and spreading thesecond frequency domain sequences in the second set with a secondorthogonal sequence, the second orthogonal sequence having a lengthequal to the number of SC-FDMA symbols in the second set.

Advantageous Effects

A scheduling request can be transmitted without interference with acontrol channel transmitting another control signal, and thus thecontrol channel can be effectively used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 is a block diagram of a transmitter according to an embodiment ofthe present invention.

FIG. 3 shows an exemplary structure of a radio frame.

FIG. 4 shows an exemplary structure of a subframe.

FIG. 5 shows an exemplary structure of a control channel in case ofusing two-dimensional spreading.

FIG. 6 shows another exemplary structure of a control channel in case ofusing two-dimensional spreading.

FIG. 7 shows a structure of an acknowledgement(ACK)/negative-acknowledgement (NACK) channel.

FIG. 8 shows an exemplary structure of an ACK/NACK channel on which ascheduling request is transmitted.

FIG. 9 shows another exemplary structure of an ACK/NACK channel on whicha scheduling request is transmitted.

FIG. 10 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted.

FIG. 11 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted.

FIG. 12 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted.

FIG. 13 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted.

FIG. 14 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted.

FIG. 15 shows a structure of a channel quality indicator (CQI) channel.

FIG. 16 shows an example of a scheduling request channel.

FIG. 17 shows an example of a scheduling request channel.

FIG. 18 shows an example of resource allocation for a scheduling requestchannel.

FIG. 19 shows another example of resource allocation for a schedulingrequest channel.

FIG. 20 shows another example of resource allocation for a schedulingrequest channel.

MODE FOR THE INVENTION

FIG. 1 shows a wireless communication system. The wireless communicationsystem can be widely deployed to provide a variety of communicationservices, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes at leastone user equipment (UE) 10 and a base station (BS) 20. The UE 10 may befixed or mobile, and may be referred to as another terminology, such asa mobile station (MS), a user terminal (UT), a subscriber station (SS),a wireless device, etc. The BS 20 is generally a fixed station thatcommunicates with the UE 10 and may be referred to as anotherterminology, such as a node-B, a base transceiver system (BTS), anaccess point, etc. There are one or more cells within the coverage ofthe BS 20.

Hereinafter, downlink is defined as communication from the BS 20 to theUE 10, and uplink is defined as communication from the UE 10 to the BS20. In the downlink, a transmitter may be a part of the BS 20, and areceiver may be a part of the UE 10. In the uplink, the transmitter maybe a part of the UE 10, and the receiver may be a part of the BS 20.

FIG. 2 is a block diagram of a transmitter according to an embodiment ofthe present invention.

Referring to FIG. 2, a transmitter 100 includes a discrete Fouriertransform (DFT) unit 110 that performs DFT and an Inverse fast Fouriertransform (IFFT) unit 120 that performs IFFT. The DFT unit 110 performsDFT on data and outputs a frequency-domain symbol. The data input to theDFT unit 110 may be a control signal and/or user data. The IFFT unit 120performs IFFT on the received frequency-domain symbol and outputs atransmit (Tx) signal. The Tx signal is a time-domain signal. Atime-domain symbol output from the IFFT unit 120 is referred to as anorthogonal frequency division multiplexing (OFDM) symbol or a singlecarrier-frequency division multiple access (SC-FDMA) symbol. SC-FDMA isa scheme in which spreading is achieved by performing DFT in a previousstage of the IFFT unit 120. The SC-FDMA scheme is advantageous over anOFDM scheme in terms of decreasing a peak-to-average power ratio (PAPR).

FIG. 3 shows an exemplary structure of a radio frame.

Referring to FIG. 3, the radio frame includes 10 subframes. One subframeincludes two consecutive slots. One slot can include a plurality of OFDMsymbols in a time domain and at least one subcarrier in a frequencydomain. The slot is a unit of radio resource allocation in the timedomain. For example, one slot can include 7 or 6 OFDM symbols.

The radio frame structure is shown for exemplary purposes only, and thusthe number of subframes included in the radio frame or the number ofslots included in the subframe or the number of SC-FDMA symbols includedin the slot may change variously.

FIG. 4 shows an exemplary structure of a subframe. The subframe may bean uplink subframe.

Referring to FIG. 4, the subframe can be divided into two parts, i.e., acontrol region and a data region. Since the control region and the dataregion use different frequency bands, frequency division multiplexing(FDM) has been achieved. The control region is a region allocated with acontrol channel. The data region is a region allocated with a datachannel. The control channel may use one resource block in each of twoslots in a subframe. A resource block includes a plurality ofsubcarriers. The control channel is a channel for transmitting a controlsignal. The data channel is a channel for transmitting the controlsignal and/or user data. The control channel is referred to as aphysical uplink control channel (PUCCH). The data channel is referred toas a physical uplink shared channel (PUSCH). The control signal may havevarious types, such as, an acknowledgement(ACK)/negative-acknowledgement (NACK) signal, a channel qualityindicator (CQI), a precoding matrix index (PMI), a rank indicator (RI),a scheduling request, etc.

The control channel transmits only the control signal. The data channelcan transmit the user data together with the control signal. Accordingto a single subcarrier property, one UE cannot transmit the controlchannel and the data channel simultaneously.

The control channel can be frequency-hopped in a slot unit on asubframe. The control channel uses different subcarriers for each sloton the subframe. A frequency diversity gain can be obtained bytransmitting the control channel through slots allocated to differentfrequency bands. It will be assumed that one subframe consists of a 1stslot and a 2nd slot. In addition, the 1st slot is divided into a 1stregion and a 2nd region in a frequency domain, and the 2nd slot isdivided into a 1st region and a 2nd region in the frequency region.Then, the control signal is transmitted through the 1st region of the1st slot and the 2nd region of the 2nd slot within one subframe.

Now, a structure of an uplink control channel will be described.

Frequency spreading and two-dimensional spreading of time-domaincovering can be applied to the uplink control channel. A referencesignal can be defined for coherent detection.

For clear explanation, it will be assumed hereinafter that one slotconsists of 7 OFDM symbols, and thus one subframe including two slotsconsists of 14 SC-FDMA symbols in total. The number of SC-FDMA symbolsincluded in one subframe or the number of SC-FDMA symbols included inone slot is shown for exemplary purposes only, and thus the technicalscope of the present invention is not limited thereto.

FIG. 5 shows an exemplary structure of a control channel in case ofusing two-dimensional spreading.

Referring to FIG. 5, {s0, s1, . . . , s13} denotes a control signalsequence for SC-FDMA symbols, and {x0, x1, . . . , x13} denotes atime-domain sequence for SC-FDMA symbols. The time-domain sequence fortime-domain spreading may use a well-known orthogonal sequence such as aWalsh code. {c0, c1, . . . , c11} denotes a frequency-domain sequencefor frequency-domain spreading. The time-domain sequence is a sequencewhose elements correspond to SC-FDMA symbols. The frequency-domainsequence is a sequence whose elements correspond to subcarriers.

A Zadoff-Chu (ZC) sequence is one example of a constant amplitude zeroauto-correlation (CAZAC) sequence and is used as the frequency-domainsequence. A ZC sequence c(k) with a length of N can be generated asshown below:

MathFigure 1

$\begin{matrix}{{c(k)} = \left\{ \begin{matrix}e^{{- j}\frac{\pi\;{{Mk}{({k + 1})}}}{N}} & {{for}\mspace{14mu}{odd}\mspace{14mu} N} \\e^{{- j}\frac{\pi\;{Mk}^{2}}{N}} & {{for}\mspace{14mu}{even}\mspace{14mu} N}\end{matrix} \right.} & \left\lbrack {{Math}.\; 1} \right\rbrack\end{matrix}$

where 0≤k≤N−1, and M is a root index and is a natural number equal to orless than N, where N is a relatively prime number to M. This means that,once N is determined, the number of root indices is equal to the numberof available ZC sequences. ZC sequences having different cyclic shiftvalues are orthogonal to each other. Therefore, from a ZC sequencegenerated using one root index, a plurality of orthogonal sequences canbe obtained through cyclic shift.

The ZC sequence is for exemplary purposes only. Thus, other sequenceshaving an excellent correlation characteristic can also be used as thefrequency-domain sequence.

The frequency-domain sequence can be undergone cyclic shift hopping foreach SC-FDMA symbol. That is, although each SC-FDMA is spread throughthe same frequency-domain sequence in FIG. 5, each SC-FDMA can also bespread through a frequency-domain sequence having a different cyclicshift value. This is called cyclic shift hopping. When the cyclic shifthopping is carried out, a control channel characteristic can beprevented from rapid deterioration caused by a high correlation at aspecific cyclic shift value.

FIG. 6 shows another exemplary structure of a control channel in case ofusing two-dimensional spreading.

Referring to FIG. 6, unlike the example of FIG. 5, a control signalsequence {s0, s1, . . . , s13} is spread over a frequency domain.

Now, a method of generating a scheduling request channel fortransmitting a scheduling request will be described.

The scheduling request is used when a UE requests a BS to allocate anuplink radio resource. The scheduling request is a sort of preliminaryinformation exchange for exchanging uplink data. In order for the UE totransmit uplink data to the BS, the uplink radio resource has to befirst requested through the scheduling request. When the UE transmitsthe scheduling request on an uplink control channel, the BS transmitsthe allocated uplink radio resource to the UE on a downlink controlchannel. The uplink control channel for transmitting the schedulingrequest is referred to as a scheduling request channel.

Examples of a method of generating the scheduling request channelinclude a method in which a channel (i.e., an ACK/NACK channel or a CQIchannel) for transmitting different control signals are reserved for thescheduling request and a method in which a dedicated channel is assignedfor the scheduling request. In the former method, the channel isgenerated simultaneously with a different control channel, andcompatibility with a different control signal needs to be maintained.Although the time-frequency resource is shared with the differentcontrol signal, the scheduling request can be identified by using adifferent sequence. In the latter method, a new time-frequency resourceis allocated to transmit the scheduling request.

First, a method of transmitting a scheduling request signal by using anACK/NACK channel and a CQI channel will be described. However, technicalfeatures of the present invention are not limited to the ACK/NACKchannel or the CQI channel. Thus, the preset invention can be widelyused in a control channel having a structure in which a second controlsignal (e.g., the scheduling request) can be transmitted on the controlchannel for transmitting a first control signal (e.g., the ACK/NACKsignal, the CQI, etc.).

FIG. 7 shows a structure of an ACK/NACK channel. The ACK/NACK channel isa control channel on which an ACK/NACK signal is transmitted. TheACK/NACK signal is a reception confirm signal for downlink data forhybrid automatic repeat request (HARQ). When the control signal istransmitted within a pre-assigned band, frequency-domain spreading andtime-domain spreading are simultaneously performed to increase thenumber of multiplexible UEs and the number of control channels.

Referring to FIG. 7, among 7 SC-FDMA symbols included in one slot, areference signal (or simply RS) is carried on 3 consecutive SC-FDMAsymbols in the middle portion of the slot and the ACK/NACK signal iscarried on the remaining 4 SC-FDMA symbols. The RS is carried on the 3consecutive SC-FDMA symbols located in the middle portion of the slot.The position and the number of symbols used in the RS may vary, and as aresult, the position and the number symbols used in the ACK/NACK signalmay also change.

A frequency-domain sequence is used to spread the ACK/NACK signal on afrequency domain. The aforementioned ZC sequence may be used as thefrequency-domain sequence. ACK/NACK channels can be identified by usingZC sequences each having a different cyclic shift value. The number ofavailable cyclic shifts may vary depending on channel delay spreading.

The ACK/NACK signal is spread in a frequency domain and is thensubjected to IFFT processing. Thereafter, the ACK/NACK signal is spreadagain in a time domain by using a time-domain sequence (or an orthogonalsequence). The ACK/NACK signal is spread using 4 time-domain spreadingcodes w₀, w₁, w₂, and w₃ for 4 OFDM symbols. The reference signal isalso spread using an orthogonal sequence with a length of 3.

Although it has been described that the frequency-domain spreading isperformed before the time-domain spreading is performed, this is forexemplary purposes only. Thus, the present invention is not limited tothe order of performing the frequency-domain spreading and thetime-domain spreading. The time-domain spreading may be performed beforethe frequency-domain spreading is performed. The time-domain spreadingand the frequency-domain spreading may be simultaneously performed byusing a sequence having one combined format.

FIG. 8 shows an exemplary structure of an ACK/NACK channel on which ascheduling request is transmitted. This is a case where at least onecyclic shift is reserved with the scheduling request in the ACK/NACKchannel structure.

Referring to FIG. 8, in the ACK/NACK channel, ZC sequences maintainorthogonality with each other by using cyclic shifts, and one of thecyclic shifts is reserved by transmitting the scheduling request.

For example, if a total of 6 cyclic shifts can be used, one cyclic shiftis used in transmission of the scheduling request. The number ofpossible cyclic shifts may vary, and two or more cyclic shifts may bereserved to transmit the scheduling request.

If a specific cyclic shift is used to transmit the scheduling request inthe ACK/NACK channel, the ACK/NACK signal is transmitted using a cyclicshift unused in the transmission of the scheduling request.

If a reserved cyclic shift is used for the scheduling request,time-domain covering can be used for each SC-FDMA symbol in a timedomain. In this case, for coherent detection, the number of times ofperforming time-domain spreading depends on min(the number of SC-FDMAsymbols of an ACK/NACK signal, the number of SC-FDMA symbols of areference signal). In the coherent detection, a constellation of a Txsignal (i.e., the ACK/NACK signal) is identified according to a definedreference signal. Since the number of SC-FDMA symbols of the ACK/NACKsignal is 4 and the number of SC-FDMA symbols of the reference signal is3, the time-domain spreading can be performed up to 3 times for thecoherent direction. Therefore, if one cyclic shift is used as ascheduling request signal for the ACK/NACK channel in the coherentdetection, a maximum of 3 scheduling request channels can be transmittedfor each slot.

Although it has been described that the number of root indices of ZCsequences usable in one cell is one, more UEs can transmit thescheduling request when the number of root indices increases.

Cyclic-shift hopping may be used in a cyclic shift for the schedulingrequest channel. If the cyclic-shift hopping is used for each SC-FDMAsymbol, a hopping pattern can be reserved in advance to be used.

The scheduling request channel is defined herein by using a cyclic shiftwhen a ZC sequence is used as a frequency-domain spreading code in theACK/NACK channel. However, if another sequence is used as thefrequency-domain sequence, the scheduling request channel may be definedby reserving a part of a corresponding sequence set or by reserving ahopping pattern of the sequence.

FIG. 9 shows another exemplary structure of an ACK/NACK channel on whicha scheduling request is transmitted. This structure supports both casesof with and without the use of a reference signal.

Referring to FIG. 9, the number of SC-FDMA symbols of an ACK/NACK signaland the number of SC-FDMA symbols of a reference signal are compared,and a greater value of the two is defined as the number of times ofperforming time-domain spreading usable for each cyclic shift. When thenumber of times of performing time-domain spreading of the controlsignal is different from the number of times of performing time-domainspreading of the reference signal, a smaller value of the two is usedfor coherent detection, and the other value is used for non-coherentdetection.

When the number of the SC-FDMA symbols of the control signal is 4 andthe number of the SC-FDMA symbols of the reference signal is 3, thecontrol signal has 4 time-domain spreading codes and the referencesignal has 3 time-domain spreading codes. If the non-coherent detectionis used, 4 time-domain sequences can be used as a spreading code. Threeof the four time-domain sequences may be transmitted using non-coherentdetection, and the remaining one may be transmitted using coherentdetection.

FIG. 10 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted. This is a case wherenon-coherent detection is used.

Referring to FIG. 10, since there is no need to transmit a referencesignal in non-coherent detection, sequences can be used in time-domainspreading, wherein the number of sequences corresponds to the number ofall available SC-FDMA symbols. When the number of SC-FDMA symbols foreach slot is 7, a length of a time-domain sequence is 7 and the numberof all time-domain sequences is also 7.

FIG. 11 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted. A time-domain sequence isreserved in the ACK/NACK channel and is used as a scheduling channel.

Referring to FIG. 11, at least one of time-domain sequences is reservedas a scheduling request channel for transmitting a scheduling request. Atime-domain sequence with a length of 7 is used as the schedulingrequest channel. The scheduling request may be transmitted using anunused portion in a time-domain sequence of a control signal or atime-domain sequence of a reference signal.

As for a frequency-domain sequence, the same frequency-domain sequenceof the control signal such as the ACK/NACK signal may be used. Anotherspecific sequence may be dedicatedly used for the scheduling request.

The ACK/NACK signal and the scheduling request may be identified througha divided time-domain sequence. That is, a frequency-domain sequenceassigned for ACK/NACK signal transmission is also used for thescheduling request, and the scheduling request and the ACK/NACK signalare identified through the time-domain sequence. In addition, when thesame time-domain sequence is used for both the ACK/NACK signal and thescheduling request, the ACK/NACK signal and the scheduling request maybe identified by assigning different frequency-domain sequences to theACK/NACK signal and the scheduling request.

For example, in case of supporting coherent detection, a maximum of 3time-domain sequences are present for 3 reference signals. At lease oneof the three time-domain sequences is assigned to a scheduling requestchannel. In addition, a control signal's time-domain sequence associatedwith a reference signal's time-domain sequence assigned to thescheduling request channel may be assigned to another scheduling requestchannel. The scheduling request channel supports coherent detection.

FIG. 12 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted. This is a case wheretime-domain sequences are reserved for the ACK/NACK channel, wherein atime-domain sequence with a length of 3 and a time-domain sequence witha length of 4 are both used.

Referring to FIG. 12, in the ACK/NACK channel, a scheduling requestchannel is configured by spreading the time-domain sequence with alength of 3 in a reference signal region and the time-domain sequencewith a length of 4 in a data region (i.e., an ACK/NACK signal part).

FIG. 13 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted. This is a case wheretime-domain sequences are reserved for the ACK/NACK channel, wherein atime-domain sequence with a length of 3 and a time-domain sequence witha length of 4 are separately used.

Referring to FIG. 13, in the ACK/NACK channel, the time-domain sequencewith a length of 3 is used as a scheduling request channel in areference signal region, and the time-domain sequence with a length of 4is used as a scheduling request channel in a data region (i.e., anACK/NACK signal part). By using two types of time-domain sequences forthe scheduling request channel, a maximum of 7 scheduling requestchannels can be configured. In comparison with the example of FIG. 12,UE capability increases.

In addition, a combination of the example of FIG. 12 and the example ofFIG. 13 can also be used. As described above, in the example of FIG. 12,the time-domain sequence with a length of 3 and the time-domain sequencewith a length of 4 are simultaneously used in the time domain, and inthe example of FIG. 13, the time-domain sequence with a length of 3 andthe time-domain sequence with a length of 4 are separately used.

FIG. 14 shows another exemplary structure of an ACK/NACK channel onwhich a scheduling request is transmitted. This is a case where atime-domain sequence is reserved for the ACK/NACK channel to be used asa scheduling channel. Non-coherent detection is used herein.

Referring to FIG. 14, in case of supporting non-coherent detection, atleast one of time-domain sequences with a length of 4 is assigned to ascheduling request channel. The four time-domain sequences correspond tofour SC-FDMA symbols. Unused time-domain sequences of a remainingreference signal portion can be assigned to other scheduling requestchannels. That is, by identifying a time-domain sequence of a controlsignal from a time-domain sequence of a reference signal, thetime-domain domain sequences are assigned to scheduling request channelssupporting non-coherent detection. In case of supporting coherentdetection, a time-domain spreading code of the control signal and atime-domain spreading code of the reference signal have to be paired tobe transmitted simultaneously.

FIG. 15 shows a structure of a CQI channel. The CQI channel is a controlchannel for transmitting a CQI. To ensure a sufficient symbol space,time-domain spreading is not used in CQI transmission.

Referring to FIG. 15, among 7 SC-FDMA symbols included in one slot, areference signal is carried on 2 SC-FDMA symbols spaced apart from eachother by 3 SC-FDMA symbols, and the CQI is carried on the remaining 5SC-FDMA symbols. This is for exemplary purposes only, and thus theposition and the number of SC-FDMA symbols used in the reference signalor the position or the number of symbols used in the CQI may vary. Whenquadrature phase shift keying (QPSK) mapping is performed on one SC-FDMAsymbols, a 2-bit CQI value can be carried. Therefore, a 10-bit CQI valuecan be carried on one slot. For one subframe, a maximum 20-bit CQI valuecan be carried. In addition to the QPSK, the CQI may use othermodulation schemes, e.g., 16-quadrature amplitude modulation (QAM).

The CQI is spread over a frequency domain by using a frequency-domainsequence. The frequency-domain sequence may be a ZC sequence. Unlike thetwo-dimensional spreading in the ACK/NACK channel, the CQI channel usesonly one-dimensional spreading and thus increases CQI transmissioncapacity. Although only the frequency-domain spreading is describedherein as an example, the CQI channel may also use time-domainspreading.

In the CQI channel, cyclic shifts can be reserved to be assigned to ascheduling request channel. This is the same as the example of theACK/NACK channel except for a difference in the number of SC-FDMAsymbols of the reference signal. Unlike the ACK/NACK channel, in the CQIchannel, in many cases, a less number of SC-FDMA symbols are assigned tothe reference signal. This is because spreading is not necessary over atime axis since users can be identified with sequence identification ona frequency axis. Therefore, a function of the reference signal can beachieved with only at least one SC-FDMA symbol. In case of a highDoppler effect, about 2 SC-FDMA symbols may be assigned to the referencesignal, but it is difficult to use time-domain spreading.

A time-domain sequence can be defined in order to define the schedulingrequest channel. In case of supporting coherence detection, similarly tothe ACK/NACK channel structure, about 3 SC-FDMA symbols are assigned tothe reference signal, and a control signal part and a reference signalpart may be identified when transmitted. In case of supportingnon-coherent detection, a time-domain spreading code can be definedusing a long sequence with a total length of one slot. Also in thiscase, similarly to the ACK/NACK channel, a sequence set of mutuallyorthogonal sequences such as a cyclic shift of a ZC sequence can bedefined to be used as a time-domain spreading code. The sequence set maybe a set of sequences whose mutual cross-correlation is small.

Although it has been described above that the scheduling request channelis configured to have a compatibility with a structure of the ACK/NACKchannel or the CQI channel, the scheduling request channel can beconfigured by reserving a new time-frequency resource. In case ofconfiguring a dedicated scheduling request channel, non-coherentdetection not requiring the reference signal may be used. This isbecause the scheduling request can be transmitted according to apresence/absence of transmission of the scheduling request channel sincethe scheduling request can be identified only with a presence/absence ofthe scheduling request channel. For example, transmission of thescheduling request channel can be regarded as transmission of thescheduling request. In addition, the presence/absence of the schedulingrequest can be toggled according to the presence/absence of thescheduling request channel.

FIG. 16 shows an example of a scheduling request channel.

Referring to FIG. 16, when the scheduling request channel is generatedindependently from other control channels, its design is not related tothe control channels. Thus, in this case, an arbitrary structure can beselected. In addition, unlike a case where a scheduling request channelis configured to be compliant with a conventional control channel, allcontrol channels can be used. Thus, UE capability for the schedulingrequest channel increases.

Similarly to the ACK/NACK channel, the scheduling request channel isconfigured by using two-dimensional spreading of a frequency domain anda time domain. That is, a slot is divided into two parts, and a firsttime-domain spreading is performed on a first part and a secondtime-domain spreading is performed on a second part. In other words, for4 SC-FDMA symbols (i.e., a first set) corresponding to a data part ofthe conventional ACK/NACK channel with respect to one slot, a firstfrequency-domain sequence is mapped onto each SC-FDMA symbol. In thiscase, the first frequency-domain sequence may have the same cyclic shiftfor each SC-FDMA symbol belonging to the first set or may have differentcyclic shifts. The first frequency-domain sequence is spread againthrough a first orthogonal sequence, that is, a time-domain sequence. Inaddition, for 3 SC-FDMA symbols (i.e., a second set) corresponding to areference signal part of the conventional ACK/NACK channel with respectto one slot, a first frequency-domain sequence is mapped onto eachSC-FDMA symbol. In this case, the second frequency-domain sequence mayhave the same cyclic shift for each SC-FDMA symbol belonging to thesecond set or may have different cyclic shifts. The secondfrequency-domain sequence is spread again through a second orthogonalsequence, that is, a time-domain sequence.

In the frequency-domain spreading and the time-domain spreading,different sequences may be used for each SC-FDMA symbol or each slot.That is, a cyclic shift of a frequency-domain sequence may change foreach SC-FDMA symbol and/or for each slot. A method of using anindependent scheduling request channel or a method of sharing thescheduling request channel with a different control channel may be usedin combination. Information related to configuration of the schedulingrequest channel may be reported by the BS to the UE through a broadcastchannel or the like. In a method of mapping resources for the schedulingrequest channel onto actual UEs, a range of a UE identifier (ID) may bedetermined so that UE IDs are mapped to resources for the schedulingrequest channel in a 1:1 manner according to the determined order.Although the scheduling request channel can be generated in everytransmission time interval (TTI), waste of radio resources can bereduced by regulating a period generated according to an amount of radioresource usable in the scheduling request channel.

FIG. 17 shows an example of a scheduling request channel. This is a casewhere non-coherent detection is supported.

Referring to FIG. 17, in case of supporting non-coherent detection,time-domain spreading is carried out through a time-domain sequence witha length of 7 corresponding to one slot.

FIG. 18 shows an example of resource allocation for a scheduling requestchannel. A radio resource for the scheduling request channel is assignedto an outermost portion of a control region. FIG. 19 shows anotherexample of resource allocation for a scheduling request channel. A radioresource for the scheduling request channel is assigned between acontrol region and a data region. The scheduling request channel may beassigned to a data region or may be assigned either one of the controlregion or the data region.

FIG. 20 shows another example of resource allocation for a schedulingrequest channel.

Referring to FIG. 20, the scheduling request channel is assigned to atleast one SC-FDMA symbol. A resource block (or simply RB) is a unit offrequency domain resource allocation and includes a plurality ofsubcarriers. The scheduling request channel can be transmittedthroughout the entire band similar to a sounding signal for uplink radioresource scheduling. The scheduling request channel may be transmittedalternately or simultaneously with the sounding signal.

In the scheduling request channel, resources can be allocated in a unitof resource blocks. A sequence used in each resource block may be a ZCsequence used in a control channel combined with a cyclic shift. In thiscase, a predetermined number of scheduling request channels can beconfigured, wherein the predetermined number corresponds to N cyclicshifts×X resource blocks.

One SC-FDMA symbol is used for a scheduling request channel. In detail,the scheduling request channel may be configured with one resourceblock, and a UE may be identified according to a sequence in use and aposition of a resource block in use.

Instead of allocating all resource blocks to the scheduling requestchannel, some of the resource blocks may be allocated to the datachannel.

Radio resource allocation information on the scheduling request channelcan be reported by the BS through the broadcast channel. A schedulingrequest signal may be periodically transmitted by the UE or may betransmitted in an event-driven manner. A transmission period of ascheduling request may be reported by the BS to the UE.

A method of transmitting uplink data through a scheduling requestrelated to uplink data transmission will now be described. A UE receivesradio resource allocation information regarding a scheduling requestchannel from a BS. The scheduling request channel is an uplink controlchannel and is different from a random access channel which is usedbefore synchronization between the BS and the UE is achieved yet. The UEconfigures the scheduling request channel by using the radio resourceallocation information and transmits the scheduling request to the BS onthe scheduling request channel. The BS transmits an uplink radioresource allocated according to the scheduling request to the UE on adownlink control channel. The UE transmits the uplink data by using theuplink radio resource.

A method of transmitting a scheduling request on a scheduling requestchannel is classified into non-coherent detection and coherentdetection. However, the scheduling request can be detected in practicein more various manners. A method of analyzing the scheduling request bydetermining a presence/absence of a signal and a method of identifyingthe scheduling request by using modulated signal information may also betaken into consideration.

In the non-coherent detection, a presence/absence of a schedulingrequest is determined according to a presence/absence of transmission ofa scheduling request channel. In the coherent detection, all UEstransmit scheduling request signals when scheduling request channels areallocated to the UEs. When binary phase shift keying (BPSK) modulationis used, a UE may transmit 1-bit information indicating whether ascheduling request is desired or not. When quadrature phase shift keying(QPSK) modulation is used, the UE may transmit additional 1-bitinformation together with the 1-bit information indicating whether thescheduling request is desired or not. In this case, the additionallytransmitted information may be quality of service (QoS) information orbuffer size information for facilitating a scheduling process.

Coherence detection and non-coherent detection can be used at the sametime. This is referred to as partial coherent detection. In the partialcoherent detection, only a UE desiring a scheduling request transmitsthe scheduling request rather than all UEs un-conditionally transmitscheduling requests. The UE transmitting the scheduling request maytransmit additional desired information. When the UE does not needscheduling, that is, when the UE does not require radio resource foruplink transmission, the UE ignores the scheduling request instead oftransmitting the scheduling request. Then, a receiver first determines apresence/absence of the scheduling request according to apresence/absence of a signal. If the signal exists, it is determinedthat there is the scheduling request. In a case where a transmittertransmits the scheduling request, additional information can betransmitted as signal modulation information. When BPSK modulation isused, additional information related to the scheduling request may becarried using one bit. When QPSK modulation is used, additionalinformation related to the scheduling request may be carried using twobits.

The present invention can be implemented with hardware, software, orcombination thereof. In hardware implementation, the present inventioncan be implemented with one of an application specific integratedcircuit (ASIC), a digital signal processor (DSP), a programmable logicdevice (PLD), a field programmable gate array (FPGA), a processor, acontroller, a microprocessor, other electronic units, and combinationthereof, which are designed to perform the aforementioned functions. Insoftware implementation, the present invention can be implemented with amodule for performing the aforementioned functions. Software is storablein a memory unit and executed by the processor. Various means widelyknown to those skilled in the art can be used as the memory unit or theprocessor.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

The invention claimed is:
 1. A method for transmitting a schedulingrequest in a wireless communication system, the method comprising:generating, by a user equipment, a modulation symbol by modulatingcontrol information; generating, by the user equipment, a plurality offirst sequences for a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols by cyclically shifting a base sequence;generating, by the user equipment, a plurality of second sequences bymultiplying plurality of first sequences by the modulation symbol;generating, by the user equipment, a plurality of third sequences bymultiplying the plurality of second sequences by an orthogonal sequence;and transmitting, by the user equipment, the plurality of thirdsequences to represent the transmission of the scheduling request andthe control information in the plurality of OFDM symbols, wherein eachof the plurality of third sequences is transmitted in a correspondingone of the OFDM symbols, wherein a cyclic shift value of the basesequence corresponding to each of the plurality of first sequences isdetermined based on a corresponding one of the plurality of OFDMsymbols, and wherein the orthogonal sequence is determined based on anumber of the plurality of OFDM symbols.
 2. The method of claim 1,further comprising: receiving, by the user equipment, assignmentinformation to assign a radio resource used for a transmission of thescheduling request for requesting uplink resources to be used for uplinkdata transmission.
 3. The method of claim 1, wherein the modulationsymbol is generated by using a binary phase shift keying (BPSK) or aquadrature phase shift keying (QPSK).
 4. The method of claim 1, whereinthe number of the plurality of OFDM symbols is three or four.
 5. Themethod of claim 1, wherein the base sequence is defined as a ConstantAmplitude Zero Auto-Correlation (CAZAC) sequence.
 6. A device fortransmitting a scheduling request in a wireless communication system,the device comprising: a processor; and a memory operatively coupledwith the processor and storing instructions that when executed by theprocessor cause the device to: generate a modulation symbol bymodulating control information; generate a plurality of first sequencesfor a plurality of orthogonal frequency division multiplexing (OFDM)symbols by cyclically shifting a base sequence; generate a plurality ofsecond sequences by multiplying plurality of first sequences by themodulation symbol; generate a plurality of third sequences bymultiplying the plurality of second sequences by an orthogonal sequence;and transmit the plurality of third sequences to represent thetransmission of the scheduling request and the control information inthe plurality of OFDM symbols, wherein each of the plurality of thirdsequences is transmitted in a corresponding one of the OFDM symbols,wherein a cyclic shift value of the base sequence corresponding to eachof the plurality of first sequences is determined based on acorresponding one of the plurality of OFDM symbols, and wherein theorthogonal sequence is determined based on a number of the plurality ofOFDM symbols.
 7. The device of claim 6, wherein the number of theplurality of OFDM symbols is three or four.
 8. The device of claim 6,wherein the modulation symbol is generated by using a binary phase shiftkeying (BPSK) or a quadrature phase shift keying (QPSK).
 9. The deviceof claim 6, wherein the base sequence is defined as a Constant AmplitudeZero Auto-Correlation (CAZAC) sequence.